1. Field of the Invention
The present invention relates to a cassette for housing a stimulable phosphor sheet, the cassette having various items of ID (identification) information, an ID recognition structure for such a cassette for recognizing the ID information when the cassette is loaded into a cassette loading unit, and an image information reading apparatus for reading radiation image information recorded in the stimulable phosphor sheet, thereafter erasing remaining radiation image information from the stimulable phosphor sheet, and returning the stimulable phosphor sheet into a cassette.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
When a radiation energy such as X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation, or the like is applied to a certain phosphor, it stores part of the applied radiation energy. When stimulating light such as visible light is subsequently applied to the phosphor, the phosphor emits light depending the stored radiation energy. Such a phosphor is referred to as a stimulable phosphor. A stimulable phosphor is usually used in the form of a sheet which is referred to as a stimulable phosphor sheet.
The above known system includes an image information reading apparatus which comprises a reading section for reading image information recorded on a stimulable phosphor sheet, and an erasing section for erasing remaining image information from the stimulable phosphor sheet after the recorded image information has been read. In the image information reading apparatus, a cassette housing a stimulable phosphor sheet which bears radiation image information of a subject recorded by an external exposure device is inserted into a loading section.
Thereafter, the lid of the cassette is opened, and then the stimulable phosphor sheet is taken out of the cassette by a sheet feeding mechanism. The stimulable phosphor sheet is delivered to the reading section by a sheet delivering mechanism. In the reading section, the recorded image information is read from the stimulable phosphor sheet, and then remaining image information is erased from the stimulable phosphor sheet in the erasing section, after which the stimulable phosphor sheet is placed into the cassette which has been disposed in the loading section.
The stimulable phosphor sheet usually comprises an opaque base and a phosphor layer (recording layer) disposed on the opaque base. The reading section has a stimulating light applying means for applying stimulating light to the phosphor layer and a light guiding means for collecting light which is emitted from the phosphor layer when the stimulating light is applied to the phosphor layer. The erasing section has an erasing light source for applying erasing light to the phosphor layer.
There has recently been a demand for the efficient reading of energy stored in stimulable phosphor sheets in order to reproduce the radiation image information of subjects with high image quality in various applications such as mammography. One effort that has been made to meet the demand is to employ a stimulable phosphor sheet having a transparent base. When stimulating light is applied to the stimulable phosphor sheet with the transparent base from the side of the phosphor layer, the stimulable phosphor sheet emits light from the side of the base (reverse side) as well as from the side of the phosphor layer. An image information reading apparatus which is capable of reading image information from the stimulable phosphor sheet with the transparent base has a reading section including two light guiding means that are positioned respectively on the opposite sides of the stimulable phosphor sheet, and an erasing section which applies erasing light to the stimulable phosphor sheet from the side of the phosphor layer.
As described above, there are two types of stimulable phosphor sheets, i.e., a single-sided stimulable phosphor sheet which emits light from the recording layer (phosphor layer), and a double-sided stimulable phosphor sheet which emits light from the recording layer and the base. It has been pointed out that double-sided stimulable phosphor sheets cannot be recognized in a single image information reading apparatus. Specifically, if a bar code is attached to the base of a double-sided stimulable phosphor sheet, then light applied to read the bar code passes through the base, so that the recording layer is exposed to the light that has passed through the base, and the bar code blocks part of light emitted by the application of stimulating light, resulting in a reading error. Therefore, using both single-sided and double-sided stimulable phosphor sheets together requires two image information reading apparatus dedicated respectively for the single-sided stimulable phosphor sheets and the double-sided stimulable phosphor sheets. Those two image information reading apparatus result in a higher equipment cost and a greater installation space.
It is a general object of the present invention to provide a cassette for housing a stimulable phosphor sheet, which can reliably indicate ID information of the stimulable phosphor sheet housed therein and which is highly versatile.
A main object of the present invention is to provide an ID recognition structure for a cassette for housing a stimulable phosphor sheet, which can reliably recognize ID information of the a stimulable phosphor sheet housed in the cassette when the cassette is loaded into a cassette loading unit.
Another main object of the present invention is to provide an image information reading apparatus which is capable of reading recorded image information from stimulable phosphor sheets that include single-sided and double-sided stimulable phosphor sheets, is highly versatile, can be manufactured at a low cost, and can be installed in a small space.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.